JPH10162852A - Diaphragm for redox flow battery and manufacture therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive diaphragm which has high charging- discharging efficiency and has excellent durability by using a copolymer of a monomer unit having substantially no unsaturated bond introduced from an aliphatic hydrocarbon monomer and a monomer unit on the basis of acrylonitrile, as matrix resin. SOLUTION: Resin obtained by adding hydrogen to a copolymer obtained by copolymerizing acrylonitrile and butadien, is cited as a copolymer. In this way, in the number of remaining unsaturated bonds, the iodine number is desirable to be 5 or less. It is suitable that a monomer unit on the basis of acrylonitrile is set to 20 to 50wt.% to the whole weight of a copolymer. Though molecular weight of the copolymer is not particularly limited, it is suitable to be normally set to a range of 50,000 to 500,000. In a diaphragm for a redox flow battery, a composition composed of this copolymer and an ion exchange resin is used by being stuck to a base material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a membrane for a redox flow battery having excellent durability, and more particularly to a membrane for a vanadium redox flow battery.

[0002]

2. Description of the Related Art In a redox flow battery, a positive electrode and a negative electrode battery active materials are passed through a liquid permeable electrolytic cell having a positive electrode chamber and a negative electrode chamber in which a positive electrode and a negative electrode are separated by a diaphragm, and a redox reaction is utilized. To perform charging and discharging. In general, a membrane having an ion function, for example, an ion exchange membrane is used as a diaphragm for the purpose of preventing permeation of metal ions. Various kinds of metals are considered to be used as the battery active material, but recently, a vanadium-based redox flow battery using vanadium as the battery active material (Japanese Patent Application Laid-Open No. Sho 62-62).
186473) has been proposed.

[0003] This battery is excellent in electromotive force, battery capacity, and the like as compared with the iron / chromium-based redox flow battery that has been conventionally studied. Even if the positive and negative electrode solutions are mixed with each other, they have the advantage that they can be easily regenerated by charging.

[0004]

Generally, as an ion exchange membrane, a resin that functions as a matrix without introducing an ion exchange group (hereinafter simply referred to as a matrix resin)
It is widely known that a resin composition of a resin and an ion exchange resin is attached to a substrate. Here, as the matrix resin, for example, a styrene-butadiene copolymer, an acrylonitrile-butadiene copolymer, or the like is used.

When an ion exchange membrane containing such a matrix resin is used as a membrane for a redox flow battery, the redox flow battery uses an oxidizing substance such as pentavalent vanadium ion or 3 Valent iron ions and the like act on the matrix resin in the ion-exchange membrane to cause a change in the ion-exchange resin portion, causing problems such as partial separation of the ion-exchange resin portion from the substrate. In particular, pentavalent vanadium ions have a strong oxidizing power and have caused a serious problem in durability when a general ion exchange membrane is used for a diaphragm.

Therefore, as a membrane having oxidation resistance, a perfluoro-based membrane or a polysulfone-based membrane (Japanese Patent Laid-Open No.
No. 88005).

However, the membrane proposed above does not satisfy all the required functions, and when used as an industrial membrane for a redox flow battery, the amount of permeation of metal ions is small and the charge / discharge efficiency is low. In particular, there has been a demand for an inexpensive diaphragm having high durability and excellent durability.

[0008]

DISCLOSURE OF THE INVENTION The present inventors have conducted intensive studies in view of the above-mentioned problems, and as a result, as a matrix resin, have substantially no unsaturated bonds derived from aliphatic hydrocarbon monomers. The present inventors have found that the above-mentioned problems can be solved by using a copolymer of a monomer unit and a monomer unit based on acrylonitrile, and have led to the present invention.

That is, according to the present invention, a copolymer of a monomer unit having substantially no unsaturated bond derived from an aliphatic hydrocarbon monomer and a monomer unit based on acrylonitrile, And a resin composition comprising an ion exchange resin and a resin composition comprising the ion exchange membrane adhered to a substrate.

[0010] The membrane for a redox flow battery of the present invention comprises:
Use of a copolymer of a monomer unit having substantially no unsaturated bond derived from an aliphatic hydrocarbon monomer and a monomer unit based on acrylonitrile as a matrix resin of an ion exchange membrane Is the feature. By doing so, a membrane having particularly excellent durability can be obtained as compared with a membrane in which a matrix resin having an unsaturated bond such as an acrylonitrile-butadiene copolymer is present.

In the present invention, the copolymer of a monomer unit having substantially no unsaturated bond derived from the aliphatic hydrocarbon monomer and a monomer unit based on acrylonitrile includes Known compounds consisting of each structural unit can be used without any limitation. As the aliphatic hydrocarbon-based monomer, an unsaturated aliphatic hydrocarbon, preferably an unsaturated aliphatic hydrocarbon having 2 to 9 carbon atoms is used without any particular limitation. In this case, as the unsaturated aliphatic hydrocarbon, specifically, it is preferable to use an olefin such as ethylene, propylene or butylene, or a conjugated diolefin such as butadiene or isoprene. In the present invention, the copolymer used as the matrix resin is a monomer unit derived from an aliphatic hydrocarbon-based monomer, in a state where the copolymer constitutes the monomer unit It has substantially no unsaturated bond. Therefore, when an aliphatic hydrocarbon-based monomer having a plurality of unsaturated bonds such as the conjugated diolefin is used as a copolymer component, the copolymer is further subjected to a hydrogenation treatment after the copolymerization. It is necessary to eliminate unsaturated bonds remaining in the unit based on the formula (1). The copolymer may be in any form such as a so-called AB diblock type, an ABA triblock type, or a random type. Further, it may contain a small amount of a third monomer such as divinylbenzene, methacrylic acid, and acrylic acid.

In the present invention, the copolymer of a monomer unit having substantially no unsaturated bond derived from the aliphatic hydrocarbon monomer most preferably used and a monomer unit based on acrylonitrile is used. Examples of the polymer include a resin obtained by copolymerizing acrylonitrile and butadiene, and further hydrogenating the obtained copolymer. When the copolymer having an unsaturated bond is subjected to a hydrogenation treatment, some unsaturated bonds may remain in the obtained copolymer. Usually, the number of such residual unsaturated bonds is preferably 10 or less, more preferably 5 or less in iodine value. The iodine value is represented by the number of grams of iodine absorbed by 100 g of the copolymer. When the iodine value is 10 or more, the iodine value is deteriorated by an oxidation reaction with a chemical species having oxidizing power contained in the redox flow battery solution, particularly, pentavalent vanadium.

In the copolymer of a monomer unit having substantially no unsaturated bond derived from the aliphatic hydrocarbon monomer and a monomer unit based on acrylonitrile, the content of each constituent unit Although it is not particularly limited, it is suitable that the monomer unit based on acrylonitrile is 10 to 60% by weight, preferably 20 to 50% by weight based on the total weight of the copolymer. The molecular weight of the copolymer is
Although not particularly limited, usually, 1,000 to
1,000,000, preferably 50,000-500,
It is preferably in the range of 000.

In the film of the present invention, as the components of the resin composition, a monomer unit having substantially no unsaturated bond derived from such an aliphatic hydrocarbon monomer and a monomer unit based on acrylonitrile are used. Confirmation that the copolymer with is used as a matrix resin can be performed, for example, by the following method. That is, the film of the present invention can be carried out by extracting the resin by Soxhlet extraction or the like with an organic solvent such as acetone or tetrahydrofuran, and analyzing the resin by infrared spectroscopy. The copolymer has a content of 2850 to 2 when measured by infrared spectroscopy.
A peak derived from a carbon-hydrogen bond exists around 950 cm ^{−1 and} around 1440 to 1460 cm ⁻¹ , and 2236 cm ⁻¹
A peak derived from a nitrile group exists around ^-1 . On the other hand, 1640 cm around ^-1, alkene carbon near ^970cm-1 - peak attributable to carbon double bond shows a characteristic such that substantially absent.

In the membrane for a redox flow battery of the present invention, a monomer unit having substantially no unsaturated bond derived from the aliphatic hydrocarbon monomer and a monomer unit based on acrylonitrile are used. A resin composition comprising a polymer and an ion-exchange resin is used by being attached to a substrate.
Such a film may be obtained by any method as long as it has the above configuration, but is usually obtained by the following method. That is, a monomer having substantially no unsaturated bond derived from a monomer having a functional group into which an ion exchange group can be introduced or an ion exchange group, a crosslinking agent, a polymerization initiator and an aliphatic hydrocarbon monomer. A mixture comprising a copolymer of monomer units and monomer units based on acrylonitrile,
This is a method in which an ion exchange group is introduced, if necessary, after adhering to a substrate and subjecting it to molding polymerization.

Here, as the monomer having a functional group into which an ion exchange group can be introduced or an ion exchange group, a monomer which is conventionally used in the production of an ion exchange membrane can be used without any particular limitation. You. Specifically, styrene,
Α, β, vinyltoluene, vinylxylene, acenaphrene, vinylnaphthalene, α-halogenated styrene, etc.
β'-trihalogenated styrene, chlorostyrenes and the like. Particularly in the case of a membrane for a cationic redox flow battery, α-halogenated vinyl sulfonic acid,
α, β, β′-halogenated vinyl sulfonic acid, methacrylic acid, acrylic acid, styrene sulfonic acid, vinyl sulfonic acid, maleic acid, itaconic acid, styrene phosphonylic acid, maleic anhydride, vinyl phosphoric acid, and their salts; Esters and the like are used. In the case of a diaphragm for an anionic redox flow battery, vinyl pyridine, methyl vinyl pyridine, ethyl vinyl pyridine, vinyl pyrrolidone, vinyl carbazole, vinyl imidazole, amino styrene, alkyl amino styrene, dialkyl amino styrene, trialkyl amino styrene ,
Methyl vinyl ketone, chloromethyl styrene, acrylamide, acrylamide, oxime, styrene, vinyltoluene and the like are used.

As the cross-linking agent, a conventionally known monomer used in the production of an ion exchange membrane is used without any particular limitation. Specifically, for example, m-, p-, o-
Examples thereof include divinyl compounds such as divinylbenzene, divinylsulfone, butadiene, chloroprene, isoprene, divinylnaphthalene, diallylamine, triallylamine, and divinylpyridines, and trivinyl compounds such as trivinylbenzenes.

Further, as the polymerization initiator, a conventionally known polymerization initiator is used without any particular limitation, and may be appropriately selected according to the base material used and the molding conditions. For example, benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, tert-butylperoxy-2-ethylhexanoate, lauryl peroxide, stearyl peroxide, methyl isobutyl ketone peroxide,
Cyclohexane peroxide, o-methylbenzoyl peroxide, 2,4,4-trimethylpentylperoxy-phenoxyacetate, α-cumylperoxy neodecanoate, di-tert-butylperoxy-
Hexahydroterephthalate, tert-butylperoxybenzoate, diisopropylbenzene hydroperoxide, di-tert-butylperoxide,
1,1-bis-tert-butylperoxy-3,3
5-trimethylcyclohexane or the like is used.

In the present invention, the above-mentioned mixture of a monomer having a functional group into which an ion-exchange group can be introduced or an ion-exchange group, a crosslinking agent, a polymerization initiator and the matrix resin may be added as necessary. As a monomer having a functional group capable of introducing an ion exchange group and a monomer copolymerizable with a crosslinking agent, for example, styrene, acrylonitrile,
Ethyl styrene, vinyl chloride, acrolein, methyl vinyl ketone, maleic anhydride, salts or esters thereof, itaconic acid, salts or esters thereof, and the like may be appropriately mixed. In addition, a plasticizer such as dioctyl phthalate, dibutyl phthalate, tributyl phosphate, tributyl acetyl citrate or an aliphatic acid or an alcohol ester of an aromatic acid, and a solvent for diluting the monomer are appropriately added thereto. Is also good.

In the present invention, the mixing ratio of each of the above-mentioned components is not particularly limited, but generally, it is based on 100 parts by weight of a functional group into which an ion exchange group can be introduced or a monomer having an ion exchange group. On the other hand, 1 to 100 parts by weight of a crosslinking agent, copolymerization of a monomer unit having substantially no unsaturated bond derived from the aliphatic hydrocarbon monomer and a monomer unit based on acrylonitrile It is preferable to blend the coalescing in the range of 2 to 200 parts by weight and the polymerization initiator in the range of 0.1 to 30 parts by weight based on 100% by weight of the total monomers.

The monomer mixture obtained as described above is adhered to a substrate and polymerized. Here, as the base material, those which use polyvinyl chloride, polyolefin or the like as a material resin, which has been conventionally used as a base material for an ion exchange membrane, are used without any limitation. As a shape, a woven fabric, a nonwoven fabric, a net, or a porous sheet thereof can be used without limitation.

The thickness of these substrates is not particularly limited, but is in the range of 10 to 200 μm, especially 50 to 12 μm.
Those having a thickness of 0 μm are preferred.

When the monomer mixture is adhered to the above-described base material and then polymerized, the temperature is generally raised from normal temperature under pressure, but the rate of temperature rise is not particularly limited and may be appropriately determined. Just choose. These polymerization conditions also depend on the type of polymerization initiator involved, the composition of the monomer mixture, and the type of base material, and cannot be determined unequivocally, but are optimal for the performance of a redox flow battery diaphragm. May be appropriately selected in consideration of the above. In addition, as a method of attaching the paste-like material to the base material, a known method such as coating, impregnation, or dipping may be appropriately adopted.

The film-like polymer obtained by the above polymerization may be used, if necessary, by subjecting it to a known method such as sulfonation.
Chlorosulfonation, chloromethylation and amination, quaternary ammonium basification, quaternary pyridinium basification,
A desired ion-exchange group can be introduced by a treatment such as phosphonium conversion, sulfonium conversion, hydrolysis, and protonation to obtain a membrane for a redox flow battery.
The introduction amount of these ion exchange groups is not particularly limited,
Usually, it is suitable that the ion exchange capacity is in the range of 1 to 20 mmol / g-dry membrane, preferably 2 to 6 mmol / g-dry membrane. Further, the thickness of the ion exchange membrane is related to desired charge / discharge efficiency, electric resistance, mechanical strength, durability, and the like, but is generally 10 to 200 μm, preferably 50 to 200 μm.
Preferably, it is in the range of 120 μm.

In the present invention, the ion exchange membrane obtained as described above is used as a membrane for a redox flow battery. The term “redox flow battery” used here refers to a method in which a battery active material of a positive electrode and a negative electrode is passed through a liquid-permeable electrolytic cell having a positive electrode chamber and a negative electrode chamber in which a positive electrode and a negative electrode are separated by a diaphragm, and utilizing an oxidation-reduction reaction. It performs charging and discharging. Battery active material combinations include iron / chromium,
Vanadium / vanadium-based, chromium / bromine-based, vanadium / titanium-based, vanadium / iron, zinc / iron-based and the like are considered. In particular, the membrane for redox flow batteries of the present invention is a battery system containing vanadium and has excellent durability.

[0026]

The membrane for a redox flow battery according to the present invention can be prepared by using a copolymer of a monomer unit based on acrylonitrile and a specific aliphatic hydrocarbon-based unit as a matrix resin constituting the membrane. Extremely excellent durability can be imparted without lowering the charge / discharge efficiency.

[0027]

EXAMPLES Examples of the present invention and comparative examples are shown below, but the present invention is not limited to these examples.

Example 1 100 parts by weight of 4-vinylpyridine, about 5 in purity as a crosslinking agent
Paste mixture obtained by mixing 5 parts by weight of 7% divinylbenzene, 2 parts by weight of benzoyl peroxide as a polymerization initiator, and 20 parts by weight of a hydrogenated acrylonitrile-butadiene copolymer having an iodine value of 4 as a matrix resin. Was coated on a polyvinyl chloride woven fabric, and covered with a polyester film as a release material, followed by heat polymerization at 75 ° C. for 6 hours.

Next, the obtained film-form polymer was treated with a 40% by weight methyl iodide solution in hexane at 30 ° C. for 24 hours.
2. Time methylation, thickness 100 μm, exchange capacity 3.
A 5 mmol / g-dry membrane for an anionic redox flow battery was obtained. This redox flow diaphragm was subjected to Soxhlet extraction at 40 ° C. for 3 days using tetrahydrofuran as a solvent, and the obtained extract was analyzed by infrared spectroscopy. As a result, 2850-2950 cm ^-1
Near, carbon vicinity 1440~1460cm ^-1 - there is a peak derived from hydrogen bonding, there is a peak derived from the nitrile group near 2236cm ^-1, on the one hand, 1640C
In the vicinity of m ^-1 and 970 cm ^-1 , substantially no peak derived from the carbon-carbon double bond of the alkene was observed.

Next, the obtained membrane for redox flow batteries was used as a positive electrode solution at 2 mol / l of VOSO ₄ +2 mo.
1 / l sulfuric acid mixed solution was used as a negative electrode solution at 2 mol / l of V
Charge / discharge was performed at a current density of 60 mA / cm ² using a mixed solution of ₂ (SO ₄ ) ₃ +2 mol / l sulfuric acid, and the charge / discharge efficiency was determined. The results are shown in Table 1. Furthermore, in order to examine the durability, as an accelerated test, it was immersed in a 1 mol / l pentavalent vanadium sulfate solution at 60 ° C. for 3 months. The immersion film did not change its shape as compared with the blank film. Table 1 also shows the results of measuring the charge / discharge efficiency of the immersion film.

Comparative Example 1 An ion exchange capacity of 3.5 mmol / g-dry membrane was obtained under the same conditions as in Example 1 except that an unhydrogenated acrylonitrile-butadiene copolymer having an iodine value of 250 was used as a matrix resin. Thus, a membrane for an anionic redox flow battery having a thickness of 100 μm was obtained.

The Soxhlet extraction was performed under the same conditions as in Example 1, and the extract was subjected to infrared spectroscopy.
A peak derived from a carbon-hydrogen bond exists around 0-2950 cm ^{-1 and} around 1440-1460 cm ^-1 , and 223
A peak derived from a nitrile group exists around 6 cm ⁻¹ ,
Furthermore, 1640 cm around ^-1, in the vicinity of ^970cm-1,
There was a peak due to the alkene carbon-carbon double bond.

The charge and discharge efficiency of this film was measured under the same conditions as in Example 1. The results are shown in Table 1. Further, as a result of immersion under the same conditions as in Example 1 in order to examine the durability, the resin component was partially peeled off. Table 1 also shows the charge / discharge efficiency of the immersion film.

Example 2 100 parts by weight of styrene, 3 parts by weight of divinylbenzene, 20 parts by weight of acrylonitrile, 20 parts by weight of dibutyl phthalate, 2 parts by weight of benzoyl peroxide, and hydrogenated acrylonitrile having an iodine value of 4 as a matrix resin A paste-like mixture obtained by mixing 15 parts by weight of a butadiene copolymer is applied to a polyvinyl chloride cloth, and a polyester film is coated as a release material.
Heat polymerization was performed at 100 ° C. for 5 hours.

Next, the obtained film-like polymer was immersed in a 1: 1 mixture of 98% concentrated sulfuric acid and chlorosulfonic acid having a purity of 90% or more for 60 minutes at 40 ° C. to obtain a film having a thickness of 100 μm.
m, an exchange capacity of 3.1 mmol / g-a dry membrane for a cation-type redox flow battery was obtained. This membrane for redox flow batteries, using tetrahydrofuran as a solvent,
Soxhlet extraction was performed at 40 ° C. for 3 days, and the obtained extract was analyzed using infrared spectroscopy. As a result, 28
Around 50-2950 cm ^-1 , 1440-1460 cm ^-1
In the vicinity, a peak derived from a carbon-hydrogen bond exists, and 22
There is a peak derived from the nitrile group near 36cm ^-1, on the one hand, 1640 cm around ^-1, in the vicinity of ^970cm-1, alkene carbon - peak attributable to carbon double bond was not substantially observed .

Next, the charge / discharge efficiency of the obtained membrane for a redox flow battery was measured under the same conditions as in Example 1. The results are shown in Table 1. Furthermore, to check the durability,
Was immersed in a 0.2 mol / l pentavalent vanadium sulfate solution for 1 month. Even after one month, no change was observed in the immersion film itself. Table 1 also shows the charge / discharge efficiency of the immersion film.

Comparative Example 2 The same conditions as in Example 2 were used except that the matrix resin was an unhydrogenated acrylonitrile-butadiene copolymer having an iodine value of 250, and a thickness of 100 μm and an exchange capacity of 3.1 mmol / g-. A dry membrane for a redox flow battery was obtained. The charge and discharge efficiency of this film was measured under the same conditions as in Example 1. The results are shown in Table 1. Further, as a result of immersion under the same conditions as in Example 2 in order to check the durability, the resin component was partially peeled off. Table 1 also shows the charge / discharge efficiency of the immersion film.

Example 3 50 parts by weight of 2-vinylpyridine, 50 parts by weight of 4-vinylpyridine, divinylbenzene 1 having a purity of about 57% as a crosslinking agent
0 parts by weight, 2 parts by weight of benzoyl peroxide as a polymerization initiator, and hydrogenated acrylonitrile-butadiene copolymer 2 having an iodine value of 4 as a matrix resin
The paste-like mixture obtained by mixing 0 parts by weight was applied to a polyvinyl chloride woven fabric, coated with a polyester film as a release material, and then subjected to heat polymerization at 75 ° C. for 6 hours.

Next, the obtained film-like polymer was treated with a hexane solution containing 40% by weight of methyl iodide at 30 ° C. for 24 hours.
2. Time methylation, thickness 100 μm, exchange capacity 3.
A 0 mmol / g-dry membrane for an anionic redox flow battery was obtained. This redox flow battery membrane was subjected to Soxhlet extraction at 40 ° C. for 3 days using tetrahydrofuran as a solvent, and the obtained extract was analyzed by infrared spectroscopy. As a result, 2850-2950
around cm ^-1, the carbon vicinity 1440~1460cm ^-1 - there is a peak derived from hydrogen bonding, there is a peak derived from the nitrile group near 2236cm ^-1, on the one hand, 16
Near 40 cm ^-1 and 970 cm ^-1 , substantially ^no peak derived from the carbon-carbon double bond of the alkene was observed.

The membrane for redox flow batteries was charged and discharged under the same conditions as in Example 1, and the charging and discharging efficiency was determined.
The results are shown in Table 1. Furthermore, in order to examine the durability, it was immersed for 3 months under the same conditions as in Example 1. The immersion film did not change its shape as compared with the blank film. Table 1 also shows the results of measuring the charging and discharging efficiency.

Comparative Example 3 The same conditions as in Example 3 were used except that the matrix resin was an unhydrogenated acrylonitrile-butadiene copolymer having an iodine value of 250, and a thickness of 100 μm and an exchange capacity of 3.0 mmol / g-. A dry membrane for a redox flow battery was obtained. The charge and discharge efficiency of this film was measured under the same conditions as in Example 1. The results are shown in Table 1. As a result of immersion under the same conditions as in Example 1 to check the durability, the resin component was partially peeled off. Table 1 also shows the charge / discharge efficiency of the immersion film.

[0042]

[Table 1]

Claims (3)

[Claims] 1. A copolymer of a monomer unit having substantially no unsaturated bond derived from an aliphatic hydrocarbon monomer and a monomer unit based on acrylonitrile, and an ion-exchange resin. A membrane for a redox flow battery, comprising an ion exchange membrane having a resin composition adhered to a substrate. 2. The redox flow battery according to claim 1, wherein the redox flow battery is a vanadium-based redox flow battery. 3. It has a substantially unsaturated bond derived from a functional group into which an ion exchange group can be introduced or a monomer having an ion exchange group, a crosslinking agent, a polymerization initiator, and an aliphatic hydrocarbon monomer. A mixture comprising a monomer unit and a copolymer of a monomer unit based on acrylonitrile, which is adhered to a substrate and molded and polymerized, and then ion-exchange groups are introduced as necessary. The method for producing a membrane for a redox flow battery according to claim 1.